Free delivery and variably restricted return valve



Jan. 14, 1969 5 MARCO 3,421,545

FREE DELIVERY AND VARIABLY RESTRICTED RETURN VALVE Filed Feb. 28, 1967INVENTOR. W .4. ,9 mm.

x? ATTORNEY United States Patent ABSTRACT OF THE DISCLOSURE A valvehaving a generally axially pivotable valve plug to permit free flow offluid in one direction through an orifice in the valve when the plug ispivoted away from its seated position. The valve plug is also mounted tobe selectively moved transversely of the axis of the orifice to a numberof set positions for variably restricting the flow of fluid in thereturn direction as desired, depending upon the selected position of thevalve plug.

Description of the invention This invention relates to a free deliveryand variably restricted return valve, and particularly to a valvesuitable for permitting relatively free flow of pressure fluid from apump to a hoist cylinder to hoist a load and for restricting the returnof fluid at various controlled rates, dependent upon the weight of theload, so as to lower loads at safe speeds.

The valve is shown for purposes of illustration connected in thehydraulic circuit of a hydraulic hoist for providing safe rates oflowering loads thereby, its use for other purposes being apparent fromthe illustrative example.

This invention is an improvement on the load lowering valve described inmy co-pending application Ser. No. 448,919, filed Apr. 19, 1965, andentitled Load Lowering Valve for Hydraulic Hoists.

As more fully disclosed in the above-entitled application, a number ofproblems are presented in connection with hoisting and lowering of loadswith fork lift trucks.

It is desirable economically that the load be hoisted as rapidly as iscommensurate with safety and generally safe hoisting is maintained dueto the capacity of the pump and its drive. Upon lowering, however, highinertial forces are developed which make it desirable to restrict thereturn flow of the pressure fluid in a proper relation to the weight ofthe load. The rate of lowering should be reduced, relative to what itwould he were the valve fully open for free flow, as the load isincreased. However, it is also economically desirable that the load belowered as rapidly as is consistent with safety, and hence that thereturn flow through the valve be adjusted accordingly in relation to theweight of the load, the return flow being greatly restricted in case ofheavy loads and progressively less restricted in case of progressivelylighter loads.

In the above entitled application, the desirable and safe delivery andreturn flows are obtained by providing a valve having an orifice whichis normally closed or restricted by a check valve plug which permitsfree flow through the orifice from the inlet of the valves to the outletfor hoisting. Upon return flow, the plug seats and thereby restricts theorifice to preselected maximum effective orifice area for return flow.Thus the valve permits free flow for hoisting and a large, but somewhatrestricted return for rapid lowering of light loads. The plug wasarranged, however, so that it could be set for progressively greaterrestriction for progressively greater loads. This setting depends uponthe pressure of the working fluid in the valve. In the above co-pendingapplication, this setting is accomplished by means of a piston exposedto the 3,421,545 Patented Jan. 14, 1969 pressure fluid in the valve bodyand connected to the valve plug by a flexible tension applying connectoror wire which pulls the valve plug, while unseated, to set positions forreduced return flow against the force of a return spring which biasesthe valve plug to the setting for maximum return flow. The set positionsto which the plug is pulled by the piston are for progressively lessflow the farther the piston is moved by the fluid. Thus the higher thepressure of the fluid becomes, the more restricted becomes the returnflow. While this valve performs efiectively, an objection is that,should the connecting tension means between the valve and the pistonbreak during hoisting, the plug would be moved by the return springbefore seating to the least restricting position, so that the load mightbe lowered much too rapidly for safety.

The present valve is one which is designed to perform the same basicoperations as the valve of the above application, but is improved so asto fail safe. Instead of the valve plug being pulled to progressivelymore restricting positions, upon increases in load, by tensioning forcespulling it to those positions, as in the application, the valve plug ofthe present improvement is pushed or moved to progressively morerestricting positions, upon increases in load, by compressive forcesexerted on the plug by the piston. The means for pushing the plug tomore restricting positions is such that no valve failure which wouldpermit the spring to move the valve plug toward its least restrictedposition can occur.

Specific new features of the present invention, other than the fail safefeature, will become apparent from the following description whereinreference is made to the drawings, in which: 7

FIG. 1 is a top plan view of the valve embodying the principles of thepresent invention and showing diagrammatically, its connection in thehydraulic circuit of a hoist;

FIG. 2 is a vertical sectional view taken on the line 22 of FIGS. 1 and3;

FIG. 3 is a cross sectional view taken on the line 3-3 in FIG. 2; and

FIG. 4 is an exploded view of the control cylinder and piston, and thevalve plug assemblage which may be used in the present invention forconvenience in installation.

Referring to the drawings, the valve comprises a body 1 having a cavity2 into which leads an inlet 3 and from which leads outlet 4. Forconvenience in description, the inlet 3 is shown as connected in acircuit including an overload relief valve 5 and a motor driven pump 6.The outlet 4 is connected to a cylinder 7 in which is operable a piston8 having a rod 9 which is operable to hoist a load L.

Within the cavity 2, between the inlet 3 and the outlet 4, is a wall 11having an orifice 12 therein and providing a seating area in surroundingrelation to the orifice. Mounted within the cavity 2 is a check valveplug 13 which is arranged to seat on the wall 11 for restricting theeffective area of the orifice 12 through which the return fluid flows,and to be unseated by the delivery fluid to permit free flow of fluidthrough the valve from the inlet 3 to the outlet 4 from the pump to thecylinder 7. For supporting the plug for movement toward and away fromthe wall 11, the plug is mounted on a support 14 for swinging about anaxis offset from and disposed in a plane normal to the axis of theorifice 12.

A suitable spring 15 is provided for lightly biasing the valve plug 13into seating relation on the wall 11. The spring may be a coil springextending about the axis of the support 14 with one end bearing on thevalve plug and the other end bearing against, and sliding along, thewall of the cavity in which the plug is located. Since in all cases, itis desirable to have a return flow past the seated valve plug, the valveplug may be arranged so that it does not entirely close the orifice whenseated.

movable endwise of its own axis. If a notch is used, its

shape is chosen in relation to the size of the orifice 12 so that in setpositions to which the valve plug 13 is moved in a directiontransversely of the axis of the orifice 12, the desired rate of returnflow, depending upon the set position of the valve plug, is obtained.

The valve plug 13 is normally biased in a direction transversely of theorifice axis by a spring 17 toward the position in which the plug 13least restricts the orifice. Therefore, assuming that no load beingsupported by the piston 8, a relatively free flow of fluid in the returndirection through the valve can be obtained. The valve plug is moved ina direction transversely of the axis of the orifice 12, which directionis parallel to the axis of the supporting member 14, by a reciprocablecompression means.

In the form illustrated, the compression means comprise a piston,indicated generally at 18, having a head 19, and a rod which providesthe support 14. The piston is arranged so that, when driven by fluidpressure, it is driven in opposition to the spring 17 and thus forcesthe plug 13 to the right in FIG. 2 against the opposition of the spring17. It is desirable that the valve plug 13 be moved increasingly in therestricting direction for reducing the effective size of the orifice 12as the pressure in the cavity 11 increases. This adjustment of thevalve, as in the co-pending application, is effected while the valve isunseated by the introduction of fluid into the inlet 3 and therefore isnot frictionally bound in seated position against the wall 11. Thisrequires only a very light fluid pressure as the only resistance to beovercome is that of the spring 17, whereas when the plug 13 is seated bythe return flow of fluid, the differential pressure built up on thedischarge side of the wall 11 holds the plug sufliciently tightlyagainst the wall 11 so as to frictionally prevent its adjustment orchange in position in a direction transversely of the axis of theorifice 12.

The piston has a head 19 and may be guided in a cylinder 20 which may beformed in a separate plug screw fitted and sealed in a suitable bore inthe body 1. The member 14 preferably is rigid and integral and coaxialwith the piston and extends into a suitable bore 21 in a plug 22, whichis secured in a bore in the body in coaxial relation with the cylinder20. The length of the portion of the rod 14 extending into the bore 21may be sufficiently long and fit sufficiently closely to provide aneffective non- .friction seal. However, an O-ring seal 23 may beprovided, if desired. The bore 21 is open at its outer end to theatmosphere so that the outer end of the rod 21 is not subjected to thepressure fluid in the cavity. Thus, assuming that the fluid inthe cavitycan readily reach both sides of the piston, a differential in pressureis provided on the reciprocal member as a whole, the differential inpressure being equal to the area of the end of the rod or support 14 andbeing the effective pressure on the head end of the piston.

The cylinder 20 is not essential, but it does have advantages. Even ifthe piston head were directly exposed in the cavity to the pressurefluid therein without a cylinder, the differential in pressure wouldstill drive the piston to the right. However, the cylinder 20 doesprovide a guide and a means for controlling the rate of flow of fluid tothe head end of the piston. If the left end of the piston 18 wereexposed directly in the cavity, it might be too sensitive in itsresponse in many instances. The controlled rate of admission of pressurefluid to the left end of the piston head 19 in FIG. 2 is preferable andcan be obtained in a number of ways. For more rapid response, a notch 24may be provided in the head for by-passing fluid between the right andleft ends of the piston. On the other hand, if a slower response isdesired, the notch may be reduced greatly, or it may be omittedentirely, and proper selected radial clearance be provided between theperiphery of the head and cylinder wall, as indicated at 25. Theclearance may be so chosen as to permit an adequate rate of flow ofpressure fluid to and from the head end of the piston while providing adamping action to eliminate flutter and control the response of thepiston more efliectively.

It is apparent with this structure that pressure fluid delivered by thepump may flow relatively freely through the inlet and pass through theorifice 12, unseating the valve plug 13 and flowing through freely outof the outlet 4 to the cylinder 7 to hoist the load. The pressuredeveloped in the fluid system depends upon the weight of the load andthe rate at which it is being hoisted, and is reflected in the pressurein the valve cavity at the outlet side of the plug 13. As the pressureat the outlet side increases, it drives the reciprocable compressionmeans, comprising the piston 18 and rod 14 to the right in FIG. 1against the resistance of the spring 17, thus moving the valve plug 13,which is unseated during the hoisting, to progressively move torestricting positions, depending upon the increase in pressure. Thus thevalve plug 13 is being set for proper return flow for the particularload at all times during the delivery from the pump to the cylinder 7for hoisting the load. Again, when picking up a load, a very free flowthrough the valve is provided from the inlet to the outlet for rapidlyraising the piston 8 in the cylinder. In this rapid rise the pistonsuddenly is subjected to the load and the pressure rises almostinstantly to a very high degree. However, the piston 19 respondsimmediately to force the unseated valve plug 13 to the desiredrestricting position, depending upon the effective load or force on thehoist piston 9.

As soon as the hoisting by the piston 9 ceases, the pressure on oppositesides of the plug 13 tends to equalize, whereupon the spring 15 seatsthe plug, in its set position, against the wall 11. Upon reducing pumppressure or opening the circuit for free flow of the fluid pressure backto the sump, the pressure on the outlet side of the valve plug 13 seatsand frictionally binds the plug against the wall 11 in the position intowhich it has been adjusted while it was unseated.

It is apparent that this structure has an advantage over that describedin the above entitled application in that practically no valve failurecan occur due to breakage of any connection between valve plug 13 andthe piston head 19, which would allow the plug to be returned by thespring 17 to the least restricting position. Breakage in no case wouldfree the plug 13 for movement to the minimum restricting position.

For convenience in manufacture, the cylinder 20, piston 19 and plug 13can be made as illustrated in FIG. 4. The cylinder 20 may be provided ina detachable screw threaded plug 27. The piston head 19 and rod 14 maybe integral with each other or fixedly secured together. The valve plug13 may be provided with a connecting portion 26 which is offset from itsorifice restricting portion. The portion 26 may be in the form of achannel so that the plug 13 may be connected pivotally to the rod 14 bymoving the channel radially of the rod to seat the rod in the channel.Thus access of the plug 13 to the rod 14 can be gained through an openface of the valve body for radial assembly as distinguished from axialassembly.

A cover closing one side of the valve body, when secured in place,prevents the channel portion 26 from becoming detached from the rod 14.

Having thus described by invention, I claim:

1. A valve comprising a hollow body having an inlet and an outlet,

settable throttling valve means in the body including a valve seathaving an orifice, and a valve plug movable out of seated position onthe seat to permit a relatively large orifice area for flow of pressurefluid from a source through the body from the inlet to the outlet andmovable into seated position to restrict the orifice area for flow fromthe outlet to the inlet, said plug being settable, while unseated, toset positions wherein it will upon reseating, restrict the orifice areain varying degrees depending upon said set positions,

resilient means normally urging the plug to a position for maximumorifice area for flow of fluid from the outlet to the inlet,

fluid pressure operable means connected to the valve plug and arrangedto be subjected to the pressure of fluid in the body during changes insaid pressure and operable thereby to set the unseated valve plug intoset positions during increases of pressure of the fluid at the outletside of the seat, for decrescent degrees of orifice area for flow fromthe outlet to the inlet, depending upon said increases of pressure,

and means to return the valve plug to seated position while it is heldby the fluid pressure operable means in the position in which it hasbeen set before the occurrence of substantial flow of pressure fluidfrom the outlet to the inlet,

characterized in that said fluid pressure operable means comprises areciprocable compression member with one end drivingly connected to thevalve plug so as to push the valve plug in the opposite direction fromthat in which the plug is urged by the resilient means, when thepressure at the outlet side of the seat reaches a predetermined valve.

2. The structure according to claim 1 wherein the plug has an orificetherethrough alignable in diflerent degrees with the orifice of theseat, and at least one of the orifices is shaped to cause predeterminedrates of change in the flow of fluid from the outlet toward the inletpast the plug in relation to the axial position of the piston.

3. The structure according to claim 1 wherein supporting means supportthe plug for movement in one path extending generally endwise of theaxis of the orifice toward and away from said seating position by thefluid and for movement by the reciprocable member in a second pathgenerally transversely of the axis of the orifice to set positions inall positions of the plug along said one path, while the plug isunseated.

4. The structure according to claim 3 wherein the supporting meanssupport the plug for rocking about a predetermined axis in a directiontoward and away from the seat and for movement endwise of saidpredetermined axis to said set positions.

5. The structure according to claim 4 wherein said supporting means is arigid member extending generally endwise of the path of the reciprocablemember.

6. The structure according to claim 5 wherein the reciprocable member isa piston and the rigid member is a piston rod coaxial with and securedin fixed position on the piston.

7. The structure according to claim 1 wherein the reciprocable memberhas a portion at one end exposed for access to fluid in the interior ofthe body and a portion at the other end which is free from access ofsaid fluid so that the reciprocable member is driven in the directionfor pushing the valve in said opposite direction by pressure of thefluid applied on said one end.

8. The structure according to claim 7 wherein the reciprocable memberhas a shoulder facing in the pushing direction and bearing against theplug so as to transmit to the plug, in said pushing direction,compressive forces applied to the piston by the fluid in the body.

9. The structure according to claim 1 wherein a cylinder is carried bythe body, the reciprocable compression member is a piston reciprocablein the cylinder and having a rod at said one end, and duct means areprovided which connect the head end of the cylinder with the interior ofthe body.

10. The structure according to claim 1 wherein the reciprocable memberis a piston having a rod portion and being rockable about, and movableendwise of, an offset axis ofiset from the axis of the orifice and lyingin a plane normal to the orifice axis, and the plug is mounted on therod portion for rocking about said offset axis toward and away fromseated position relative to the seat in all axial positions of thepiston.

References Cited UNITED STATES PATENTS 2,886,065 5/1959 Hershrnan 138-463,146,792 9/1964- Donnelly et al. 137-5133 X 3,298,393 1/1967 Mosier137513.3

LEONARD D. CHRISTIAN, Primary Examiner.

US. Cl. X.R.

